Ascaris Lumbricoides - Giant Roundworm

Ascaris lumbricoides, giant roundworm, is the most common parasitic worm in humans. According to some
estimates 25 % of humans are infected with the disease, ascariasis. Ascariasis occurs worldwide, mostly in tropical
and subtropical countries. It has highest prevalence in areas of poor sanitation and where human feces are used as
fertilizer.

The life cycle of Ascaris lumbricoides takes about three months. Ascariasis starts,
when Ascaris lumbricoides eggs are accidentally swallowed. They can be acquired from dirty fingers, water
or food that has been contaminated with feces of an infected human. Larvae hatch from the eggs, penetrate the
intestinal wall and enter the bloodstream. They stop at pulmonary arteries and stay in the lungs for two weeks.
They break into the alveoli and travel up the respiratory system to the throat to be swallowed again. The migration
is needed for the larvae to develop into adults. Adult worms attach themselves to the intestinal wall ready to
mate. Adults survive by eating food digested by the host and live up to 2 years. A female produces about
200 000 microscopic eggs per day that are passed in feces. The eggs fertilize into infective stage within a
few weeks in the right conditions in the soil. Unfertilized eggs are not infective. The eggs are very resistant to
chemicals, extreme temperatures and other rough conditions and can survive for months. Adult females are 20–35 cm
long and 3–6 mm in diameter. Male worms are a little smaller reaching 15–30 cm in length and 2–4 mm in width.

Ascariasis can be asymptomatic, if there are only a few worms. If there are tens or hundreds of worms, symptoms
might include:

diarrhea

fever

nausea

stomach ache

slower growing of a child or a teen

vomiting

weakness.

Unlike many other human roundworms, Ascaris lumbricoides does not usually feed on blood. When larvae
migrate through the lungs, the following pulmonary symptoms may occur:

breathing difficulty

cough and/or coughing up blood

eosinophilic pneumonitis.

If you happen to vomit or defecate an adult Ascaris lumbricoides, take the worm to your health care
provider for diagnosis. Usually however, the diagnosis is done by examining your feces for the
presence of Ascaris lumbricoides eggs. Your health care provider asks you to provide stool samples for
testing.

Ascariasis is usually treated for 1–3 days with ascaricides medicine prescribed by your health
care provider. Some common drugs are albendazole, ivermectin, nitazoxanide and mebendazole, which kills roundworms
by preventing them from absorbing nutrients. You may be asked to provide additional stool samples 1–2 weeks after
the treatment to confirm that the worms are dead.

To prevent new infections:

Avoid touching soil that might be contaminated with human feces.

When traveling to areas where hygiene and sanitation are poor, avoid food and water that might be
contaminated with soil.